Men and women age 65 years and older are a rapidly growing segment of the United States population, and it is estimated that more than 20% of the population will be age 65 and over by the year 2000. While the majority continue to live independently, over 40% of people age 65+ report difficulty in performing their usual activities. Because of the personal, social, and economic costs associated with loss of function, there is much interest in identifying the relationship between age-related diseases and functional impairment. Visual impairment is an important component of functional disability in older persons, and there are consistent data that visual impairment is associated with inability to remain independent with increasing age. However most data are based on self-report of visual impairment, and there are few data on causes of visual loss of the interaction of vision impairment and other co-morbid conditions on functional status. This program project would bring together a consortium of experts in ophthalmology, epidemiology, geriatrics, psychophysics, and biostatistics to explore the prevalence, incidence, and etiologies of visual impairment in the elderly and model the complex interaction of vision with co-morbid disease in functional disability. A population-based sample of 2,300 persons age 65 to 84 (25% black and 69% female) will serve as the basis for this study. The participants will be examined twice, 20 months apart to address the following broad areas: (1) The association of specific psychophysical measures of visual impairment with specific indices of functional status. (2) The pathophysiologic causes of visual impairment and the role of the normal aging process. (3) The association of the major age-related ocular pathologies, cataract and age-related macular degeneration (AMD) with specific indices of functional status. (4) Risk factors for cataract, AMD, and keratoconjunctivitis sicca (dry eye). (5) A model for the interaction of visual impairment and other sensory impairment in balance disability. The program project will encourage a multi-disciplinary approach to this study of visual impairment, with the cost-efficient strategy of operation in a single population. The findings will provide key insights into etiologies for the major age- related ocular conditions, and a better understanding of the impact of visual impairment on functional status. Such data will lay the basis for more effective strategies for the prevention and treatment of vision loss in older persons.